The present invention relates to a scroll type compressor and more particularly to a scroll type compressor that inhibits leakage and improves compression efficiency by providing tip seals respectively on the distal ends of the scroll walls of the compressor""s fixed and movable scroll members.
Since a scroll type compressor is relatively small and has relatively high efficiency, it is widely employed in both home and vehicular air conditioners. Also, a scroll type compressor that supplies an electrode of a fuel cell (hydrogen-oxygen type) with compressed gas, such as hydrogen, oxygen and air, has been developed.
Basically, the scroll type compressor has a fixed scroll member fixed to a housing of the compressor, a movable scroll member aligned to face the fixed scroll member and a drive source, such as a motor, that drives the movable scroll member. As the movable scroll member orbits, substantially falcate compression chambers defined between the fixed scroll member and the movable scroll member move radially inwardly; that is, the compression chambers move from the outer side adjacent to an inlet of the compressor toward the center adjacent to a discharge port of the compressor, and the volumes of the compression chambers also progressively reduce. Thereby, introducing, compressing and discharging a gas are consecutively performed.
It is desired to ensure sealing performance between the compression chambers by inhibiting gas from leaking from the compression chambers. Reducing such leakage improves compression efficiency of the scroll type compressor. An axial clearance is defined between each scroll wall and a respective facing end surface of each base plate. This clearance may not be zero because of machining inaccuracies, assembly variances and vibration generated upon operation of the compressor. Therefore, reducing the axial clearance between the fixed scroll member and the movable scroll member can improve compression efficiency.
To substantially eliminate the effect of the axial clearance, tip seals are respectively provided on distal ends of the scroll walls. The tip seals are fitted and held in grooves that are respectively recessed on the distal ends and can move in the grooves. The tip seals slide on the facing end surfaces of the base plates in accordance with the orbital motion of the movable scroll member and determine the clearance between the distal ends and the respective facing end surfaces. Thereby, sealing performance between the compression chambers is ensured.
To improve compression efficiency of the compressor, not only the axial clearance but also a radial clearance is preferably as small as possible. However, since the radial clearance is defined between coadjacent side surfaces of the scroll walls, the radial clearance cannot be adjusted by providing the above-mentioned tip seal. Therefore, the clearance between the coadjacent side surfaces of the scroll walls is designed to be reduced as much as possible. As the radial clearance becomes smaller, scratching can easily arise between the coadjacent side surfaces of the scroll walls. Therefore, resin coating layers are formed on the coadjacent side surfaces of the scroll walls. Thereby, the coadjacent side surfaces of the scroll walls are inhibited from scratching and slanting.
When the resin coating layers are formed not only on the coadjacent side surfaces of the scroll walls but also on the end surfaces of the base plates, the tip seals consequently slide on the resin coating layers. When the tip seals are made of resin, coefficient of friction between the tip seals and the respective resin coating layers is relatively extremely large. Additionally, in such a state, the tip seals and the respective resin coating layers progressively abrade, with a consequence of producing a large amount of abrasion dust. An increase in coefficient of friction undesirably causes a decrease in compression efficiency of the compressor. Also, as a large amount of abrasion dust is produced, the abrasion dust undesirably causes trouble of a various kinds of bearings and valves that are disposed downstream of the compressor.
Japanese Examined Utility Model Publication No. 7-24633 discloses a scroll type compressor that includes resin coating layers only on side surfaces of its scroll walls and that does not include the resin coating layers on end surfaces of its base plates that slide on tip seals. Also, Japanese Examined Patent Publication No. 6-15867, in a scroll type compressor without a tip seal, discloses that upon sliding between resins, even if contact pressure is relatively low, coefficient of friction between the resins becomes relatively large and the amount of abrasion rapidly increases. Based on these Publications, sliding between metal and resin is preferable.
In the Japanese Examined Utility Model Publication No. 7-24633, resin coating layers are formed only on the side surfaces of the scroll walls and are not formed on the end surfaces of the base plates. Namely, the resin coating layers are not formed on the entire end surfaces of the base plates, irrespective of a sliding region of the tip seals.
Therefore, an extra clearance is defined between the distal ends of the scroll walls and the respective facing end surfaces of the base plates on the opposite side of the compression chambers relative to the tip seals, and compressed gas leaks from the relatively high pressure compression chambers to the relatively low pressure clearance. Thereby, volumetric efficiency reduces and loss of re-compression increases, with a consequence of deteriorating compression efficiency of the compressor. It is desired that compression efficiency of the scroll type compressor is improved by inhibiting gas from leaking from the relatively high pressure compression chambers to the clearance.
In accordance with the present invention, a scroll type compressor has a housing, a crankshaft, a fixed scroll member, a movable scroll member, a fixed scroll tip seal and a movable scroll tip seal. The crankshaft is supported by the housing and is connected to a drive source. The fixed scroll member made of metal is fixed to the housing and has a fixed scroll base plate from which extends a fixed scroll wall. The movable scroll member, also made of metal, has a movable scroll base plate from which extends a movable scroll wall whose wall surfaces engage the wall surfaces of the fixed scroll member in a well-known manner at moving lines of contact as the movable scroll member orbits relative to the fixed scroll member. The movable scroll member is driven by the crankshaft connected to the drive source. The fixed scroll base plate, the fixed scroll wall, the movable scroll base plate and the movable scroll wall define compression chambers. Gas is compressed by the progressively reducing volumes of the compression chambers in accordance with the orbital motion of the movable scroll member relative to the fixed scroll member. The fixed scroll tip seal made of resin is provided on a distal end of the fixed scroll wall and slides on the movable scroll base plate. The movable scroll tip seal made of resin is provided on a distal end of the movable scroll wall and slides on the fixed scroll base plate. The fixed scroll tip seal and the movable scroll tip seal seal the compression chambers. A resin coating layer is formed on the end surfaces of at least one of the movable scroll base plate and the fixed scroll base plate other than a sliding region where the fixed scroll tip seal slides and/or a sliding region where the movable scroll tip seal slides.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.